Molecular dynamics combined with dissipative particle dynamics were use to construct a model of a binary mixture in which the two species differed only in their dynamic properties (friction coefficients). A study was made of the interdiffusion process for an asymmetrical mixture of slow and fast particles. Relaxation of the composition profile was investigated in terms of its Fourier coefficients. Fickian behavior was observed for weak asymmetry, but a strongly asymmetrical system exhibited clear indications of anomalous diffusion, which occurred in a crossover region between the above cases.

Non-Fickian Interdiffusion of Dynamically Asymmetric Species: a Molecular-Dynamics Study. Yaneva, J., Dünweg, B., Milchev, A.: Journal of Chemical Physics, 2005, 122[20], 204105